Merge pull request #2134 from karalabe/save-state-writes

core/state, trie: don't leak database writes before commit

2 files changed, 127 insertions, 3 deletions

diff --git a/core/state/statedb.go b/core/state/statedb.go
index 8093472b5..22ffa36a0 100644
--- a/core/state/statedb.go
+++ b/core/state/statedb.go
@@ -206,9 +206,6 @@ func (self *StateDB) Delete(addr common.Address) bool {
 
 // Update the given state object and apply it to state trie
 func (self *StateDB) UpdateStateObject(stateObject *StateObject) {
-	if len(stateObject.code) > 0 {
-		self.db.Put(stateObject.codeHash, stateObject.code)
-	}
 	addr := stateObject.Address()
 	data, err := rlp.EncodeToBytes(stateObject)
 	if err != nil {
@@ -375,8 +372,15 @@ func (s *StateDB) commit(db trie.DatabaseWriter) (common.Hash, error) {
 			// and just mark it for deletion in the trie.
 			s.DeleteStateObject(stateObject)
 		} else {
+			// Write any contract code associated with the state object
+			if len(stateObject.code) > 0 {
+				if err := db.Put(stateObject.codeHash, stateObject.code); err != nil {
+					return common.Hash{}, err
+				}
+			}
 			// Write any storage changes in the state object to its trie.
 			stateObject.Update()
+
 			// Commit the trie of the object to the batch.
 			// This updates the trie root internally, so
 			// getting the root hash of the storage trie
diff --git a/core/state/statedb_test.go b/core/state/statedb_test.go
new file mode 100644
index 000000000..8138f8d78
--- /dev/null
+++ b/core/state/statedb_test.go
@@ -0,0 +1,120 @@
+// Copyright 2015 The go-ethereum Authors
+// This file is part of the go-ethereum library.
+//
+// The go-ethereum library is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Lesser General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// The go-ethereum library is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+// GNU Lesser General Public License for more details.
+//
+// You should have received a copy of the GNU Lesser General Public License
+// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
+
+package state
+
+import (
+	"math/big"
+	"testing"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/ethdb"
+)
+
+// Tests that updating a state trie does not leak any database writes prior to
+// actually committing the state.
+func TestUpdateLeaks(t *testing.T) {
+	// Create an empty state database
+	db, _ := ethdb.NewMemDatabase()
+	state, _ := New(common.Hash{}, db)
+
+	// Update it with some accounts
+	for i := byte(0); i < 255; i++ {
+		obj := state.GetOrNewStateObject(common.BytesToAddress([]byte{i}))
+		obj.AddBalance(big.NewInt(int64(11 * i)))
+		obj.SetNonce(uint64(42 * i))
+		if i%2 == 0 {
+			obj.SetState(common.BytesToHash([]byte{i, i, i}), common.BytesToHash([]byte{i, i, i, i}))
+		}
+		if i%3 == 0 {
+			obj.SetCode([]byte{i, i, i, i, i})
+		}
+		state.UpdateStateObject(obj)
+	}
+	// Ensure that no data was leaked into the database
+	for _, key := range db.Keys() {
+		value, _ := db.Get(key)
+		t.Errorf("State leaked into database: %x -> %x", key, value)
+	}
+}
+
+// Tests that no intermediate state of an object is stored into the database,
+// only the one right before the commit.
+func TestIntermediateLeaks(t *testing.T) {
+	// Create two state databases, one transitioning to the final state, the other final from the beginning
+	transDb, _ := ethdb.NewMemDatabase()
+	finalDb, _ := ethdb.NewMemDatabase()
+	transState, _ := New(common.Hash{}, transDb)
+	finalState, _ := New(common.Hash{}, finalDb)
+
+	// Update the states with some objects
+	for i := byte(0); i < 255; i++ {
+		// Create a new state object with some data into the transition database
+		obj := transState.GetOrNewStateObject(common.BytesToAddress([]byte{i}))
+		obj.SetBalance(big.NewInt(int64(11 * i)))
+		obj.SetNonce(uint64(42 * i))
+		if i%2 == 0 {
+			obj.SetState(common.BytesToHash([]byte{i, i, i, 0}), common.BytesToHash([]byte{i, i, i, i, 0}))
+		}
+		if i%3 == 0 {
+			obj.SetCode([]byte{i, i, i, i, i, 0})
+		}
+		transState.UpdateStateObject(obj)
+
+		// Overwrite all the data with new values in the transition database
+		obj.SetBalance(big.NewInt(int64(11*i + 1)))
+		obj.SetNonce(uint64(42*i + 1))
+		if i%2 == 0 {
+			obj.SetState(common.BytesToHash([]byte{i, i, i, 0}), common.Hash{})
+			obj.SetState(common.BytesToHash([]byte{i, i, i, 1}), common.BytesToHash([]byte{i, i, i, i, 1}))
+		}
+		if i%3 == 0 {
+			obj.SetCode([]byte{i, i, i, i, i, 1})
+		}
+		transState.UpdateStateObject(obj)
+
+		// Create the final state object directly in the final database
+		obj = finalState.GetOrNewStateObject(common.BytesToAddress([]byte{i}))
+		obj.SetBalance(big.NewInt(int64(11*i + 1)))
+		obj.SetNonce(uint64(42*i + 1))
+		if i%2 == 0 {
+			obj.SetState(common.BytesToHash([]byte{i, i, i, 1}), common.BytesToHash([]byte{i, i, i, i, 1}))
+		}
+		if i%3 == 0 {
+			obj.SetCode([]byte{i, i, i, i, i, 1})
+		}
+		finalState.UpdateStateObject(obj)
+	}
+	if _, err := transState.Commit(); err != nil {
+		t.Fatalf("failed to commit transition state: %v", err)
+	}
+	if _, err := finalState.Commit(); err != nil {
+		t.Fatalf("failed to commit final state: %v", err)
+	}
+	// Cross check the databases to ensure they are the same
+	for _, key := range finalDb.Keys() {
+		if _, err := transDb.Get(key); err != nil {
+			val, _ := finalDb.Get(key)
+			t.Errorf("entry missing from the transition database: %x -> %x", key, val)
+		}
+	}
+	for _, key := range transDb.Keys() {
+		if _, err := finalDb.Get(key); err != nil {
+			val, _ := transDb.Get(key)
+			t.Errorf("extra entry in the transition database: %x -> %x", key, val)
+		}
+	}
+}